Assessment of Methane Emissions from Anaerobic and Facultative Ponds from Domestic and Industrial Sources at Dandora Estate Sewerage Treatment Works, Nairobi City County, Kenya
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Date
2025-03
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Kenyatta University
Abstract
Methane gas is odorless and colorless, and causes greenhouse gas effect and is up to 100 times more potent than carbon dioxide in capturing energy at lower atmosphere in the first 5-year duration, and 72 times more in the next 20 years. The goal of this study was to quantify the amount of methane emission from anaerobic and facultative ponds at Dandora Estate Sewerage Treatment Works. Dandora Estate Sewerage Treatment Works is located 30 kilometers to the East of Nairobi City County. The treatment plant receives municipal wastewater of domestic and industrial composition for treatment mainly through wastewater stabilization ponds. This process, however, leads to production of three important greenhouse gases; methane, nitrous oxide and carbon dioxide. Due to the importance in reduction of greenhouse gases, it is critical to understand the processes responsible for these emissions. This study focused on the following objectives: i) to analyze how methane production is affected by typical wastewater quality parameters such as pH, Biological Oxygen Demand, Chemical Oxygen Demand, Total Organics in the Wastewater and temperature; ii) to assess how the performance of Dandora Estate Sewerage Treatment Works ponds affects methane emission; and iii) to assess the trend of methane emission from the anaerobic and facultative ponds at Dandora Estate Sewerage Treatment Works between the years 2007 to 2017. This study used the Intergovernmental Panel on Climate Change (IPCC) methodology of 2006 in assessment of methane emission. There were two anaerobic ponds, six primary facultative ponds, eight secondary facultative ponds and twenty-two maturation ponds making a total of 38 ponds. A laboratory research design was employed to measure the amount of biological oxygen demand, chemical oxygen demand, total solids, temperature, pH, dissolved oxygen, and wastewater inflow and outflow volumes. It was estimated that anaerobic ponds emitted into the atmosphere 3.2641X107 kg CH4/yr from domestic wastewater sources and 5.5053X104 kg CH4/yr from industrial sources. Facultative ponds emitted into the atmosphere 1.5176X107 kg CH4/yr from domestic wastewater sources and 3.9176X104 kg CH4/yr from industrial sources. Methane emission was significantly affected by typical wastewater parameters. The performance of the ponds in breaking down organic components in the wastewater was significantly proportional to methane emission. The trend of methane emission between the years 2007 and 2017 showed a correlation of 0.915 between anaerobic and facultative ponds methane emission from industrial wastewater sources. Mean methane emission from domestic wastewater from anaerobic and facultative ponds had a correlation of 0.67. Optimization of wastewater parameters such as temperature, pH, total solids, biological oxygen demand, chemical oxygen demand and dissolved oxygen significantly influenced methane emission and is important in effective biogas production system. It is therefore recommended that methane gas be captured for electricity production.
Description
A Thesis Submitted In Partial Fulfilment of the Requirement for the Award of the Degree of Master of Environmental Science in the School of Agriculture and Environmental Science, Kenyatta University, March 2025.
Supervisors
1. Simon Maingi
2. Gathu Kirubi